CHEM125-C                                                                                                  Fall, 2005

Hourly Exam # 4                                                                                             Dunnivant

 

Name (PRINTED) ____________________________________

 

There are 100 points.

 

The honor statement must be signed in order for your exam to be graded.

Closed book, closed Internet, closed notes, closed neighbor!

I have neither given nor received aid on this exam.  

                                                            Signature ________________________

 

NOTES:

-Show all work for partial credit.  

-Significant figures and units will be graded throughout the exam.

 

 

  1. (10 pts) Calculate the absolute temperature of 4.79 x 10-2 moles of an ideal gas occupying 135 mL at 720 torr (there are 760 torr per atm).

 

 

  1. (10 pts) You graduate from graduate school and go car shopping.  You donŐt give a crap about the environment and buy a dual-tank BIG truck.  The tanks hold a total of 55.5 gallons as gasoline that is primarily composed of C8H18.  How much CO2 vapor do you create each time you burn the contents of your gas tanks?  Assume 1.00 atm pressure, 25.0 oC, and that the density of the gasoline is 0.850 g/mL.  There are 3.785 L/gallon.  In answering this question complete a flow chart for all reactants and products.  If you cannot figure out all of this problem, show me how to set it up with all relevant equations, etc. for partial credit.

 

 


  1. (10 pts) Using PV=nRT as a starting point derive an equation for calculating the density of a gas.

 

 

  1. (10 pts) You have equal moles of two gases, HF and CO2 at the same temperature and pressure.

 

a)     Which compoundŐs molecules will have the highest root mean squared velocity?

 

 

b)    Which gas will condense the easiest (first) upon cooling?

 

 

c)     Which gas can undergo hydrogen bonding?

 

 

d)    Which gas will diffuse at a greater rate?

 

 

e)  Which gas (if any) has the greater volume?

 

 

 

  1. (10 pts)

a)     What is the difference between intramolecular and intermolecular forces?

 

 

b)    What gives water its unique properties?

 

 

c)     Why do gasoline and water not mix?

 

d)  Why is helium put in the breathing air of deep sea divers?  Explain!

 

 

  1. (10 pts) You are walking in the woods on a cold fall day and come upon a pond that is covered with mist rising from the water. 

How is the mist formed?

 

Which direction is energy flowing in the terrestrial, pond, atmospheric system?

 

 

Give two criteria that a molecule of water must have to evaporate.

 

 

Where will ice first form in the pond and why?  (be careful!)

 

 

Explain the origin of surface tension that allows Jesus bugs to walk on water.

 

 

  1. (10 pts)

a)      Name/Give two criteria that a gas must have to be IR active (absorb infrared radiation).

 

 

b)    Name 5 gases that are IR active.

 

 

c)     Name 5 potential affects of global warming (natural or human-made)

 

 

d)    Give two major affects of the oceanic conveyor belt (circulation) shutting down?

 

 

  1. (5 pts) Name five success stories of our environmental policies (and they donŐt necessarily have to be the same five I named in class but that MUST be success stories).

 

 

  1. (5 pts) Name three pollutants that have decreased in concentration in the U.S. over the past 30 years.

 

 

  1. (3.33 pts each) Explain the following using the figure given below:

 

What is the reason for a difference in light intensity for the upper-most and lower-most lines in the figure (the two solid lines)?

 

 

What do the shaded regions represent?

 

 

Draw a line on the x-axis representing the visible region of the spectra.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



  1. (5 pts)  Draw a figure illustrating the radiation coming into the Earth and radiation being emitted back into space.  Use this figure to explain global warming and the transformation of electromagnetic radiation that occurs.

 

 

  1. (5 pts) Draw a figure showing the rough concentration of atmospheric CO2 as a function of time, going back 160000 years.  Add todayŐs data and projections for CO2 in the next 50 to 100 years.  Why are most scientists concerned about this?  Be specific.